Blade Idea: High-RPM Rotating LED Strip Blade

So I came across this post by JAM41 where he links a spinning volumetric display (led array). This got me thinking… Could you make a whole blade spin fast enough such that it looks like a uniformly lit cilinder?

This is basically what I mean, but for individual leds:
(1) Simple Spinning LED Light - YouTube
(1) How to make fast spinning RGB LED lights. - YouTube

Schermafbeelding 2024-01-22 132326
So imagine a lightweight frame with two already diffused, high-density COB strips on the sides with round foam (or something) in the middle to mitigate drag at high RPMs. You could use a slip ring connector to have the blade spin freely on some bearing-stabilized carbon fiber tube, powered by a 5VDC motor.

Goodbye diffusers, goodbye overheating (because aircooled, even with drag reducing measures). As an added bonus the blade might even produce some sound at higher speeds. It’s pretty far out there but I haven’t seen anything like it on the web and I think it could work. Any thoughts?

@profezzorn commented on the linked post with a similar idea - this is just my take on it.

What is the foam for?
Wouldn’t you still need a diffuser to deal with the space between LEDs?

Here’s an example of a COB LED strip with 320 leds/m. I’ve only seen them with diffusers and from what I’ve seen IRL you can’t distinguish the individual leds at all, even with fewer leds/m (but only at higher brightnesses).

The foam in my sketch is to keep the lightweight frame from generating too much drag while spinning, i.e. spinning a long plate versus spinning a cilinder. This should improve the efficiency and lead to higher RPMs.

Maybe you can also build some kind of spinning construction inside a PC tube, which would make it more protected and potentially more stable. If you do it right you could actually make the blade itself be transparant/see-through :eyes: :eyes: :eyes:. For example by creating the spinning frame out of acrylic. Wouldn’t that be something :stuck_out_tongue_winking_eye:

Why not just use a carbon fiber tube?

Could also work I guess, probably better to start simple indeed.

(Solution focus respose)

(Problem focus response)
Swinging a rapidly spinning blade could be a problem due to the gyro effect. It wouldn’t take a very strong drag to twist it out of angle when you do rapid spins.
Keeping the blade lightweight helps, but rotational momentum can be a real pain when you try to move rapidly spinning things around.

My idea based on a high power beam-expanded laser at the base and a liquid-filled blade with fluorescent dye (Rhodamine 6G) doesn’t sound as complicated any longer by comparison…
Still illegal, though. Lasers with several watts output are dangerous things, spread-out LED light sources are much safer.
I also recall toying with chemoluminescence, which would have required lethal oxidizing chemicals to sustain the reaction, like chlorine dioxide. Truly nasty stuff, that. The advantage is that chemoluminescence produces almost no heat at all. Think party glow-sticks, only with 1000x the power and sustained operation.

I’m curious about the gyroscopic forces. Initial reaction says it should be manageable if you keep the weight down and don’t spin the blade faster than necessary.

I remember reading about your laser and chemoluminescence ideas. The laser is interesting but if you use a cloudy liquid you’re going to lose luminosity with distance, so a simple base-lit saber would do the trick already. Let’s not talk about injecting laser light at multiple points with optics… Also instead of spreading the laser light with optics you could mount a diode on a spinning platform and create a cylinder shape that way (edit: you’d need an extremely powerful laser if you want the beam to be visible in air, of course…). Probably more difficult to cool though and you need to stop the light at a certain point or you’re going to instigate an actual star war.

The chemolum idea is cool but very impractical and dangerous haha. 1m long glowstick! But instead of chemoluminescence, you might be able to use phosphorescence. Basically just make a TL lamp, like a translucent tube coated with phosphorescent material on the inside along with a string of blacklight leds (which you won’t be able to make out because it’s blacklight).

Personally though, I wouldn’t want to replenish anything other than electric charge, so chemicals and evaporative coolants (as discussed in the other thread) are a no-go for me. I like the R&D talk here but in the end it’s pretty easy to get something that outshines the competition and makes a good impression while being practical. Spinning blade is still on the table for me though :stuck_out_tongue:

Two other types of tech I’ve been thinking about are those flickering bulbs used in electric chandeliers or last-century christmas decorations, called unstable cathode glow, and neon tube lighting (or mercury argon, which is used nowadays). Last one is a bit of a hassle though, because you’re dealing with:

  1. Low pressure vessle you need to isolate
  2. ~15kVAC to energize the noble gas, all contained in a conductive metal hilt you hold in your hand
  3. The high power consumption and heat produced

I might try rebuilding my melted plain green blade, seal the LED strip core to be waterproof by a transparent shrink-wrap tube, and add a heat conducting fluorescent liquid to diffuse the light instead of the heat insulating foam diffuser. Rhodamine 6G is soluble in water and converts green light to yellow light with a very high efficiency, and it’s a reasonably cheap chemical. I also happen to have a small bag of it already. Perhaps a circulation pump is just overkill. I keep forgetting that a light saber is meant to be used only in rather short bursts.

If you have time to spend you should totally try it out (but document results of course :)), it would be very interesting to know if it works or not. Remember, the whole point of R&D is trying weird shit and seeing if you can get it to work; the initial crazzines of the idea is of no relevance. Take it from a guy who works at the company that pioneered EUV photolithography, spending billions of euros and centuries of man hours to pass megawatt 13.5nm wl laser pulses through a vacuum mirror assembly 50.000 times a second which, against all odds was made to work.

Also, tonic (royal club, Schweppes) emits a blueish hue under EUV light which might be interesting to look at.

That’s from quinine.
I don’t think it’s a very strong fluorescence though.

If the fluorescence happens inside a light guide, like a liquid-filled PC tube, even a weak fluorescence will catch a large amount of photons. But rhodamine 6G is more dependable, and it has its absorptipn maximum in green wavelengths. Polycarbonate deteriorates rapidlyin strong UV light, so I would think pumping the fluorescent dye with visible wavelengths is a better option.

Incidentally, I was involved with the design of the early UV flash exposure units from Micronic Laser Systems. My work was on the rendering side, trying to render and push thousands of frames per second to a mirror array. We made that work, too.
These days, the work could be done by a few standard GPU chips, but this was 20 years ago…

So, you don’t have to convince me of the value of crazy experiments! :grin:

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